1. Field of the Invention
The present invention relates to imaging means such as document copiers, printers, and fax machines; and more particularly to the document exposure area of such imaging apparatus.
2. Description of the Prior Art
Imaging apparatus such as document copiers, for example electrophotographic copying machines, wherein a document to be reproduced is manually placed upon an exposure platen located at the top of the machine and exposed onto a photosensitive medium are well known in the art. To protect the machine operator from the exposure illumination and to block ambient light from the copying mechanism of the machine, a light cover is frequently provided for placement over the document and the exposure platen during the exposure process. Copiers of this type are advantageously employed to reproduce single documents or the pages of a book.
It is also known in the art to attach a document feeder to the frame or housing of such copiers for use in applications in which a large number of discrete documents are to be copied. The document feeder transports the documents in a programmed sequence to the exposure platen, actuates the copiers to reproduce the documents, and then feeds the documents to an output receptacle. A description of a document feeder accessory for use with copiers of the above mentioned type, can be found in U.S. Pat. No. 3,499,710 to Sahley. As disclosed in this patent, the document feeder has a frame supported on the copiers so that at least a portion thereof overlies the exposure platen and the overlying portion can be readily moved away from the exposure platen to a non-use position to provide for manually positioning a book or the like on the platen.
In its operative position overlying the exposure platen, the document feeder itself functions as a light cover to block the entrance of ambient light and to shield the exposure illumination and is to be included in the meaning of the phase "light cover" as used herein. However, when the document feeder is moved to a non-use position away from the exposure window to permit the exposure of books or individual documents, the ambient light surrounding the exposure platen may reduce the quality of the reproduction produced by the copier and an operator subjected to the exposure illumination may find the illumination irritating or even harmful.
It has been suggested in commonly assigned U.S. Pat. No. 3,726,589 to provide a retractable light cover positionable over the exposure platen when the document feeder is moved to its non-use position. The retractable light cover is stored wrapped on a spring loaded storage spool mounted within the housing of the copying machine when the document feeder is in its operative position overlying the exposure platen. When the document feeder is moved to its non-use position, the light cover may be pulled out to cover the exposed platen.
While such apparatus is an effective light shield, it is somewhat awkward and time consuming to use, particularly when many pages of a book or books are to be copied.